> Nobody on this list nor any of us question  your experience and ability to
> survive closed circuit electronically controlled rebreathers, especially
> experimental ones. You have successfully  “dodged the bullet” longer than
> anyone still living and we all respect you for both your luck and acumen.
> Still, this story you have recounted is shocking in that it
> demonstrates the
> extreme danger of computer controlled CCRs and the deadly sequence of
> compounded errors which unwittingly can lead to an untimely demise.

I agree.  With luck, the Wak2 divers all got the same message.  This being
the message I have always told:  that rebareathers require discipline, and
that complacency, either on the part if the instructor or the diver, can be
deadly.

> 1.) The unit in question had bad batteries and you claim that the
> batteries
> provide power to the
> O2 addition solenoid, yet you did not replace them. “Part of my
> strategy was
> to not replace batteries on the appropriate schedule, such that they would
> experience actual battery
> failures during the course of their dives. “  (Does Bill Stone recommend
> that you do this to students on the CIS in anything other than a swimming
> pool?)

The idea was all mine. Neither Bill nor Tom Mount were especially
comfortable with the idea, but since it was basically a swimming pool
environment, and since the divers had been doing so well, I allowed myself
to have greater confidence in their abilites.  I wanted to give them the
lesson I learned from diving with a prototype machine, which is:
"Electronics should never be considered life-support".  I didn't even let
them turn the power on until the third or fourth day.  That part I think
went well.  My mistake was then throwing too much at them at once after I
did let them turn the power back on. It's a mistake I don't intend to ever
repeat.

> How do you explain what you say next ?  “At this point, he
> apparently
> decided to let the solenoid bring the PO2 back to his setpoint of
> 0.5.” (no
> battery power, no o2 yet somehow the solenoid will bring the PO2 back to
> normal .. whaaatt??)

The diver did not know that the battery would fail at that time (nor did I).
I did not emphasize strongly enough to the students that they should
manually keep the PO2 out of the red zone at all times ("red zone" meaning
less than about 0.4 or 0.5).  I had a lot of information to pass on, and
this is one of the few items that slipped through the cracks.  That very
morning I cautioned the divers that now that they were getting comfortable
on the units, they were entering the most dangerous part of their rebreather
diving careers - the point at which confidence exceeds abilites, and
complacency starts to creep in.  Guess I was right about that much at least.
Anyway, in discussing the issue with the other divers after the incident,
had that message not been loud and clear before, it certainly was now.

> Then you say later that  “The first is that the
> solenoid battery died, which is a very real possibility because I
> deliberately did not change it when I was supposed to, and is supported by
> the fact that the surface team member did not recall hearing the solenoid
> fire after removing the rebreather from the diver. “  (I would gather that
> the solenoid didn’t fire, but what difference would it make if the gas
> supply to the solenoid was disabled anyway? See #2) THIS DOES NOT COMPUTE
> RICHIE.

Not sure I see your point here, Bill.  Either the battery failed, or the
diver had the supply disabled, or possibly both.  In any case, the solenoid
was not adding O2 to the loop - that much is obvious.  Diver error,
electronics failure, whatever - it shouldn't matter.  The incident should
not have happened, but it did, because a bunch of little things, any one of
which is very minor, compounded into an accident.  That's exactly how people
can die on these things. I threw too much at them at once, and a bunch of
unfortunate coincidences came together and kicked us in the ass.  That's why
I think it's so important that people be open about sharing mistakes with
others.  I learn the most from my own mistakes, but I also learn from the
mistakes of others.  I know you never make any mistakes, so you probably
wouldn't understand this.  By the way, as much as George would like to take
credit for "flushing" this out, the fact is, I had already made the decision
to post the incident long before.  In fact, the decision was made shortly
after the incident, and solidified on the plane flight home.

> 2.) The addition gas supply to the solenoid was disabled. “Also,
> as part of
> their drills, I
> had asked them to disable the gas supply to the solenoid, to
> practice manual
> control of the rebreather.” Again I ask you to explain the above. “At this
> point, he apparently decided to let the solenoid bring the PO2 back to his
> setpoint of 0.5.”

Maybe I wasn't clear enough.  I gave them a series of drills to practice.
One of those drills was to disable the solenoid pneumatically to simulate a
failed battery. Another drill was to flush the loop with new diluent.  The
first of these was done the previous day.  However, I encouraged them to
practice other previous drills on subsequent dives. Hence, it may have been
the case that prior to doing the loop flush, he was practicing with a
simulated disabled solenoid.   I never told them to do them both at the same
time. The diver does remember simulating the disabled solenoid earlier in
the dive, but can't be certain that he re-enabled it before the hypoxic
incident.  The solenoid battery appeared to work fine after the incident -
but this may have been due to a short-lived refresh of the lithium battery
that powers the solenoid.  In any case, most of this is moot because the
incident should not have happened in the first place.  But it did, so now
the best we can do is try to learn as much from it as we can.

> Then you say later on that ” The second is that the
> diver inadvertently left the solenoid O2 supply disabled
> during a previous practice drill (can't be sure, because he can't
> remember,
> and also because he later used the same valve to try to get O2 to the OC
> mouthpiece).”  (Which is it? He purposely turned it off or he
> didn’t really
> know?) THIS DOES NOT COMPUTE RICHIE.

Again, I think I missed your point - or maybe you missed mine.  As I said
above, he purposely turned it off earlier in the dive as a practice drill,
but he can't be certain that he re-enabled it.  At present, my money is on
the failed battery, because the diver in question is very good, and would
not likely have made such a mistake.  Moreover, the solenoid did not appear
to be firing when we got the rig off of him.  Maybe it was both - well never
know for sure.  But my point, which I keep emphasizing, is that NEITHER of
these failures should have led to the problem. That they did is more a
reflection of my inexperience in the role of instructor than anything else.

> 3.) You “figured” that “the depth was about 25-30 feet and the
> heliox would
> be safe and breathable on the bottom”.  Not for very long, at best, unless
> the oxygen addition system was functioning, which apparently it wasn’t and
> you or the student was unaware of this. You are also aware that
> the mass  of
> oxygen in the closed circuit breathing loop for 14% heliox is trifling at
> 1.5 ATA. You are also aware, or should be that it is very
> difficult, if not
> physiologically impossible, to breath the loop ppo2 to below .17
> before you
> pass out.

Not sure where you are going with the first bit, but as to the last
sentence, well, the term "horseshit" comes to mind.  It's comments like this
that reveal your true lack of actual experience on these things.  Generally
people don't even start to feel subtle symptoms until the inspired PO2 drops
to below 0.15 or so (except in high exertion situations, or for prolonged
periods of time).  In situations where exertion is low, and time is on the
order of a few minutes (as was the case on the incident in question), severe
symptoms don't become manifest until about 0.07, and blackout doesn't
usually happen until 0.06.  Again, this is low exertion, with gradual drop
in inspired PO2.  This isn't from any book - this is from watching people do
hypoxia tests time and time again.  Every one of the divers did such a test
the day before.  Every one went to 0.07 before even noting serious symtpoms.
Some went to 0.05.  None blacked out.  Tell me, where did you pull the 0.17
number from?  Some book, I assume.

> 4.)   The unit has a “miscalibrated” o2 sensor. Whatever “miscalibrated”
> means.

It means that one of the sensors was reading about 0.1 atm higher than the
other two - just on the borderline of being voted out under the current
circumstances.  It was that way for the previous dive as well. I could
easily have recalibrated it, but opted instead to let the diver get used to
a simulated flakey sensor.

> Since the unit never added any o2, based on the final
> reading of the
> logged loop pp02, I guess the sensor was severely “miscalibrated” or
> somebody or something was “miscalibrated”.

More evidence for your lack of understanding of how these things actually
work.  The miscalibrated sensor had *NOTHING* to do with the failure to add
O2 to the loop, because it was voted out (as it should be).  The only role
it played was to cause periodic flashing of the system light on the Heads up
Display, which might have contributed to the diver not noticing the flashing
O2 heads up display light (a different light).  Like I said, the Heads Up
display was doing what it was supposed to: alerting the diver of an
out-of-range sensor. This sort of thing only happens in a training
environemtn, when the instructor deliberately leaves the sensor out of
calibration.  Again, comes back to me throwing too much at them too soon.
This is the lesson I hope people are getting out of this.

> 5.) At the surface you say that . “The diver later told me that he was
> trying to switch the manifold
> such that his OC regulator would have pure oxygen - a very clever response
> under the circumstances. I figured he must have had some sort of problem
> with his rebreather, so”  and  “He tried to switch his OC supply
> to 100% O2,
> but didn't engage it all the way.”  Would this response have been
> clever if
> the diver was at 300’ (the depth of the Wakulla system)?

Obviously, if he was at 300 feet, he wouldn't have done this.  He only did
it because he knew the heliox was borderline hypoxic at his shallow depth.
Of course, at 300 feet, heliox-14 would have a PO2 of 1.4, which would have
eben pretty-much the same as O2 at his depth.  He was "clever" because, in
spite of his impared state, he was able to think all of this through, even
though I have NEVER suggested that a hypoxic diver should do this in an
emergency.  The reason he didn't get it all the way is that it is a
procedure that involves a very deliberate action with both hands
simultaneously.  This is intentionaly specifically to PREVENT switching to
open-circuit O2 at depth.  The only time a diver would ever want to get O2
to the OC mouthpiece in a hurry is essentially the exact situation he was
in, which, as I emphasized, should never have been the case.

> It is unconscionably dangerous to simulate hypoxic conditions even on a
> supervised diver, in the water.

I agree - I have strongly opposed any attempts to intentionally do this in
the water.  I only do it on the surface with several people standing by, and
plenty of O2 on hand.  The only reason I thought the diver might have been
doing this intentionally is that he was in OC mode and ascending.  I figured
he got 0.2 in the loop at depth, then switched to OC and ascended so he
could see how the alarms responded to a hypoxic loop PO2.  Had he been on
closed-circuit at the time, I would have been all over him, but since he was
on OC, and showed no overt signs of stress, I maintained myself as an
observer.

> It is extremely irresponsible to
> “simulate”
> these conditions on an unsupervised diver.

I TOTALLY agree!

> Richie, your final admission is a telling one, in part because of the
> obvious truth and the unusual candor.

Thank you - George called it a "bullshit coverup", but you seem to think I
am telling the truth.

> “As for my errors, I've learned some valuable lessons which I will not
> likely
> forget. “

I will say it again over and over. The most important one is to remember
that students do not have the inate understanding of the system that the
instructor does (or should have).  I am used to being in the water only with
people of equal or greater experience.  I guess this is the sort of thing I
need to pay close attention to if I ever enter the instructor arena.

> “As for the diver's errors, the first two were really more my fault than
> his,
> and the third is not certain.”

Again, I'll say it again and again - but I think it was a very specific set
of circumstances (namely, my intentional effort to not change batteries and
not recalibrate O2 sensors).  I still think my concept has merit - which is,
teach the students the failure modes first, then let them try a fully
functioning unit.  However, I will obviously implement this concept with
MUCH greater caution in the future.

> “As for the rebreather's errors, the first, if it was real, was my fault.
> The second wasn't a rebreather fault per se, because the heads-up-display
> did exactly what it was supposed to. Had the erroneous sensor been”
>
> (Did Bill Stone dictate the last one to you?  I notice that the rebreather
> has been absolved of wrongdoing and we are back to “diver error” or “diver
> trainer error”)

Believe me, I wanted NOTHING more than to blame the rebreather, or the
diver.  Don't misinterpret my willingness to discuss my shortcomings as an
indication that I enjoy doing so.  I have an ego too, and as someone who
wants to learn how to teach certain sorts of skills, it's very difficult for
me to admit I have a long way to go before I am ready. The suggestion that I
would let Bill Stone influence my report is highly insulting, but since I
know you don't mean it, and you are just trying to get me to play the game
(which I already said I don't have time to do), I won't hold it against you.
For the record, I had a brief conversation with Bill a few hours after the
incident to tell him what happened, but have otherwise not spoken with him
at all about the incident since then.  I got one email from him this morning
asking for a report of the week's activities (which I haven't been able to
get to yet, because of all this nonsense).  My only response to him was to
forward him a copy of the report that I sent to the rebreather list, which
has predictably been forwarded on to other lists, presumably for political
reasons.

> RICHIE. Let’s be frank here.  The real error was getting into the water in
> the first place with the thing.

Bill, I'm happy being Frank, but I thought that was George's job (i.e.,
Bama).  However, I'd like to ask that you not be stupid.  The previous
comment was nothing but stupid.

> What you have recounted here are a mixture of human and machine problems
> which make rebreathers and in particular CCRs so dangerous.

Yes, and I have known and preached this for years.

> Now
> just imagine
> if this situation occurred several thousands of feet back at  280 – 300 ft
> in Wakulla.  What would you do then if a warning light went off,
> if you even
> happened to notice it?

Either correct the problem, or OC bailout. I have done the former many, many
times.  I have done the latter only once, and then only temporarily until I
could do the former.  Hypoxia isn't my biggest concern at 300 feet.
Hyperoxia is the bigger concern.

> Your little open circuit bailout is useless out
> there and you are not providing external scuba open circuit
> bailout.

Who is not providing external OC bailout?

> This is
> not a hypothetical scenario, because the express purpose of this
> exercise is
> to train these people to do just that, DIVE WAKULLA.

Wrong again.  The express purpose of this excercise was to allow me to pass
on what I know about how to stay alive under adverse circumstances on the
MK-5.  By most accounts, I apparently achieved this purpose.

> History seems to repeat itself with these CCRs. I seem to remember Kenny
> Broad describing  a flashing red warning light on the rebreather of Ian
> Rollin when he found him, dead, in Huatla. Sort of like the
> telltale heart.

Yup, that is true.  Unfortunately for your case, everyone I have spoken with
(including Kenny), corroborated by the downloaded data that I have
personally seen, is certain that hypoxia did not lead to Ian's death.  I
realize you don't want to accept that, and that's O.K. by me.  Unlike that
incident, the recent one I was involved with was clearly instigated by
hypoxia (again, corroborated by the downloaded log data). So there are
different lessons to be learned.

Thanks for your engaging discourse.  I hope my response has satisfactorily
answered your queries.  If not, please feel free to ask more questions.  As
I said, however, I will ignore the stupidity and invitations to play the
game with you, because I really do have other things to do.

Aloha,
Rich

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